On crank, the starter cable is likely to have between 400 and 1000 amps of current running through it. This test
uses an amp clamp to view the crank amperage. The allowed voltage drop depends on the crank amperage.

NOTE: This test may require an assistant.
Starter Path Check – Checks 5a, 5b, and 5c – EPA07 only
5a - Measuring crank amperage with amp clamp
5a.1 Place an amp clamp on the positive starter cable, set it to read current between 400 and 1000 amps, and
zero it. Make sure the ammeter can read, and is set to read, this range before proceeding. See Fig. 9.

Page 6

Freightliner Service Bulletin, 8/31/2017

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional

> Century Class Conventional
> Argosy COE
Cargo
> Columbia
> 122SD and Coronado

02/17/2017

54-278
Freightliner
Service Bulletin

> Business Class M2
> Cascadia
> 108SD/114SD
> New Cascadia

f151191

Fig. 9, Measure the crank amperage with an amp clamp
on the positive starter cable during crank.

5b - Starter positive cable voltage drop test
5b.1 Clip the DMM to the threaded portion of the positive post on the starter and the positive lead base of one
of the batteries.
5b.2 Crank the engine. After the voltage reading normalizes (about 2 to 3 seconds), but before the engine
starts, record the voltage drop shown on the DMM.

IMPORTANT: Do not crank for longer than 30 seconds. Allow the starter to cool for 2 minutes
between crank events.
5c - Starter negative cable voltage drop test
5c.1 Clip the DMM to the threaded portion of the negative post on the starter and the negative lead base of one
of the batteries.
5c.2 Crank the engine. After the voltage reading normalizes (about 2-3 seconds), but before the engine starts,
record the voltage drop shown on the DMM.
Combine the voltage drop of the positive and negative cable voltage drop tests. Look up the crank amperage
recorded using Table 2; total voltage drop from the two tests should not exceed the value given. If total voltage
drop is greater than the allowed voltage, go to Check 6, then test voltage drop again. If total drop is within the
allowed value, go to Check 6 but do not retest voltage drop.
Max. Acceptable Combined V Drop by Amperage
Max. Acceptable
Amps
Combined V Drop
375-449
0.6
450-549
0.7

Freightliner Service Bulletin, 8/31/2017

Page 7

54-278
Freightliner
Service Bulletin

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional

> Century Class Conventional
> Argosy COE
Cargo
> Columbia
> 122SD and Coronado

> Business Class M2
> Cascadia
> 108SD/114SD
> New Cascadia

Max. Acceptable Combined V Drop by Amperage
Max. Acceptable
Amps
Combined V Drop
550-624
0.8
625-724
0.9
725-799
1.0
800-874
1.1
875-974
1.2
975-1025
1.3
Table 2, Max. Acceptable Combined V Drop by
Amperage
6.

Check all cable connections for corrosion and torque. Repair or replace if needed, then test again.

Check 6 – Check all cable connections for corrosion and torque. See Fig. 10 and Fig. 11. Repair or
replace if needed, then test again.
Loose connections can cause intermittent problems as well as higher resistance, and are likely to have
corrosion. Most battery labels will specify the torque value; if the torque value cannot be found, use 10 to 15
lbf·ft (13 to 20 N·m).

06/24/2013

f151194

Fig. 11, Check the battery connections for looseness
and corrosion. Check the torque on the connections.
02/17/2017

f151192

Fig. 10, Check the positive post on the starter solenoid
for loose cables and corrosion.

Page 8

Freightliner Service Bulletin, 8/31/2017

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional

> Century Class Conventional
> Argosy COE
Cargo
> Columbia
> 122SD and Coronado

54-278
Freightliner
Service Bulletin

> Business Class M2
> Cascadia
> 108SD/114SD
> New Cascadia

ADDITIONAL BATTERY LOADS CHECK
Key-off Loads
7. Key off, Load Disconnect Switch set to "Off" (if equipped). Wait 10 minutes for all loads to
stop.
Set amp clamp to a lower range setting. Zero amp clamp away from the vehicle.
For each POS cable leaving batt pack, clamp the cable and record the amperage.
If more than 1.0 amp, find sources of drain and remedy as needed.

Rec
Value
+
+
+
=

Accept
Value
Add amps.
Total must
be less than
1 amp.

Check 7 – Detail, Key-off Loads Check
A key-off load is an electrical load that still draws current from the batteries when the ignition remains off, and in
some cases, when the load disconnect switch is off. Some devices, such as the engine controller, the antilock
braking system (ABS), and the radio memory, are intended to draw a very low current continuously. In long-term
parking situations, however, these drains may discharge the batteries enough to cause a no-start condition.
Key-off loads tend to be measured in milliamps (mA).
7.1 Set the Load Disconnect Switch to "Off." Shut the door, and wait 10 minutes after shutting the door for all
"keep-alives" (signals sent between devices) to turn off.

NOTE: On vehicles with a SAM module, the SAM will wake up for a self-check after 30 minutes of
inactivity, then turn off.
7.2 Zero the amp clamp away from the vehicle to ensure that all battery draw—including "background"
current—is detected upon measurement. The amp clamp should be set to a lower range, sensitive setting.
7.3 For each positive cable leaving the battery pack, clamp the cable and record the amperage. See Fig. 12.
Add the amperages together. If the total is more than 1.0 amp, find the sources of drain and remedy as needed.

Freightliner Service Bulletin, 8/31/2017

Page 9

54-278

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter

Freightliner
Service Bulletin

FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional

02/17/2017

> Century Class Conventional
> Argosy COE
Cargo
> Columbia
> 122SD and Coronado

> Business Class M2
> Cascadia
> 108SD/114SD
> New Cascadia

f151195

Fig. 12, After zeroing the amp clamp away from the
vehicle, measure the amperage in each positive cable
leaving the battery pack.

Finding Sources of Battery Drain
Pull fuses individually on the circuit with the highest draw until the total combined amperage drops below 1.0
amp. From there, find the component on that particular circuit drawing the additional current. Repair or replace
as needed.

NOTE: Opening and shutting doors will wake up system keepalives. If a door is opened during the
procedure, wait 10 minutes after closing the door before measuring draw.
NOTE: The LVD (low voltage disconnect) could be bypassed by inverters or other aftermarket
installed systems.

Key-on Loads
8.

Amp clamp on POS alt cable. ENG at IDLE, turn on driver’s normal use loads.
If load is more than 80% rated amps, find sources of draw and/or upgrade alternator.
Retest after remedying.

Rec
Value

Accept
Value
Total less
than 80%
rated amps.

Check 8 – Key-On Loads Check
This test looks at the "normal use" loads of the vehicle during normal operation conditions by measuring draw at
the alternator positive cable. "Normal use" should include high beams, radio, blower, and additional driver
accessories.

Page 10

Freightliner Service Bulletin, 8/31/2017

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional

> Century Class Conventional
> Argosy COE
Cargo
> Columbia
> 122SD and Coronado

54-278
Freightliner
Service Bulletin

> Business Class M2
> Cascadia
> 108SD/114SD
> New Cascadia

At idle, the total load should not be above 80% of the alternator’s rated output (e.g. 270 amps x .80 = 216
amps). See Table 2 for 80% load by alternator amperage rating. If the normal use load is higher, then a number
of related issues can be at play that are outside the scope of this troubleshooting topic. These might include
high-draw loads, and circuit voltage drop (from corrosion, looseness, or damage).
Max. Acceptable Key-on Load by Alternator
Amperage Rating
Amp
Max. Load
135
108
160
128
185
148
200
160
240
192
270
216
275
220
Table 3, Max. Acceptable Key-on Load by
Alternator Amperage Rating

If all systems are functioning properly, but the normal use load exceeds the alternator rating, either a higher
rated alternator should be installed, or non-essential high-draw loads should be permanently removed from the
system.

CHARGING SYSTEM CHECK - ALTERNATOR

Engine
Throttle
9a. DMM on POS and NEG of batt pack. (Undercharge check) IDLE
9b. DMM on POS and NEG of batt pack. (Overcharge check) PARTIAL
9c. DMM on POS and NEG of batt pack. (Overcharge check) WIDE OPEN
Carbon Pile:
DMM:
10a.POS and NEG of batt pack.
POS and NEG of batt pack. PARTIAL
10b.POS and NEG of batt pack.

Key
Position
KEY ON
KEY ON
KEY ON

Carbon
Rec
Pile
Value
NO LOAD
NO LOAD
NO LOAD

70% of alt
KEY ON rated
70% of alt
POS and NEG of batt pack. WIDE OPEN KEY ON rated

Accept
Value
13.2-14.8 V
13.2-14.8 V
13.2-14.8 V
Within .2 V
of Check 9
Within .2 V
of Check 9

Checks 9a and 9b – Under and Overcharge Checks
9a. With a DMM, probe any battery in the primary battery pack at the negative and positive lead bases of the
battery posts. With the engine running at idle and no loads turned on, record the voltage at the pack.
9b. With the engine running at partial throttle and no loads turned on, record the voltage at the pack.
9c. With the engine running at wide open throttle and no loads turned on, record the voltage at the pack.
In both cases, the voltage should be above 13.2 V, and higher than it was before starting the engine. If not, the
alternator is undercharging, and should be replaced.
If the voltage reads above 14.8 V, the alternator is overcharging the batteries. Check the remote sense circuit
before condemning the alternator.

Freightliner Service Bulletin, 8/31/2017

Page 11

54-278
Freightliner
Service Bulletin

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional

> Century Class Conventional
> Argosy COE
Cargo
> Columbia
> 122SD and Coronado

> Business Class M2
> Cascadia
> 108SD/114SD
> New Cascadia

Check 10 – 70% of Rated Output Check
10a.1 With a DMM, probe any battery in the primary battery pack at the negative and positive battery posts.
10a.2 Clamp the carbon pile to the positive and negative battery pack leads.
10a.3 Place an amp clamp around the positive alternator cable. The amp clamp will be used to measure the
total draw on the alternator from the carbon pile and other system loads. See Fig. 13.

02/17/2017

f151197

Fig. 13, Use an amp clamp around the positive
alternator cable to measure the draw of the carbon
pile.

10a.4 With the engine running at partial throttle, adjust the carbon pile until the amp clamp reads 70% of the
alternator rated amperage (e.g. 270 amps x .70 = 189 amps). See Table 4. With this load applied, record the
voltage at the battery pack.
10b. With the engine running at wide open throttle, adjust the carbon pile until the amp clamp reads 70% of the
alternator rated amperage (e.g. 270 amps x .70 = 189 amps). See Table 4. With this load applied, record the
voltage at the battery pack.
While the load is applied, the voltage reading on the DMM should not drop more than 0.2 V below the reading
in step 9b (the partial throttle, no load condition). If the voltage difference is more than 0.2 V, replace the
alternator, then perform tests 9a, 9b, and 9c again to verify the repair.

IMPORTANT: The voltage will drop if the carbon pile is drawing more than 70% of the alternator
rating. Do not replace if a low voltage reading was seen with a load above 70%. Instead, test again
with 70% of the alternator’s rated load.
Target Carbon Pile Amp Draw by Alternator Rating
Use Carbon Pile Draw of
Alternator Rating (Amp)
(Amp)
135
95
160
112
185
130
200
140
240
168
270
189

Page 12

Freightliner Service Bulletin, 8/31/2017

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional

> Century Class Conventional
> Argosy COE
Cargo
> Columbia
> 122SD and Coronado

54-278
Freightliner
Service Bulletin

> Business Class M2
> Cascadia
> 108SD/114SD
> New Cascadia

Target Carbon Pile Amp Draw by Alternator Rating
Use Carbon Pile Draw of
Alternator Rating (Amp)
(Amp)
275
193
Table 4, Target Carbon Pile Amp Draw by
Alternator Rating

Remote Sense Check
11a.DMM on Rem Sense post, NEG on alt GND.
11b.DMM on POS of alternator, NEG on alt GND.

Key
Engine
Position
ENG OFF KEY OFF
ENG OFF KEY OFF

Carbon
Rec
Pile
Value
NO LOAD
NO LOAD

Accept
Value
Less than
.05 V diff

Remote Sense
The remote sense circuit allows the alternator to directly measure battery voltage, in addition to the
measurement it takes from the large cables. With these two voltage measurements, the alternator calculates the
amount of voltage drop over the large cables and adjusts its output to provide the at-battery regulated voltage.
Freightliner vehicles come equipped with either Delco Remy or Leece-Neville alternators, most of which have
remote sense.
Checks 11a and 11b – Remote Sense Check
11a. With the key off, place the DMM probes at alternator ground and remote sense post/terminal. See Fig. 14.
Record the voltage.
11b. Place the DMM probes at the alternator body and the positive post of the alternator. Depending on the